Today, more and more paints are produced which are water-based and completely free from organic solvents, such as glycol ethers. When toning these paints to the desired colour, use is made to a great extent of pigment dispersions, which can be used both for water-based paint and for paint based on organic solvents. The pigment dispersions are normally composed of pigments, fillers, dispersing agents and an aqueous phase in the form of ethylene glycol, di- and triethylene glycol, propylene glycol, dipropylene glycol, tripropylene glycol and glycerol. In most cases, the dispersing agent is a nonionic surface-active compound or a combination of nonionic and anionic surfactants. For environmental reasons, it is however desirable that the pigment dispersions are solvent-free.
U.S. Pat. No. 4,156,616 discloses a pigment dispersion containing as surface-active components an aminoethoxylate and an anionic surface-active compound. As liquid phase, alkylene glycols or formamide are used in the Examples.
European Patent 84 645 discloses a solid pigment preparation which is completely solvent-free and consists of pigments and a nonionic alkylene diamine to which propylene oxide and then ethylene oxide have been added.
European Patent Application 49 785 discloses a pigment dispersion containing inorganic pigments, an alkylene oxide adduct, a copolymer and water or a mixture of water and a water-retaining agent. The alkylene oxide adduct may consist of, for instance, a reaction product between ethylene oxide and a phenol, alcohol, carboxylic acid, carboxylic acid amide or alkyl amine. In all Examples, at least one organic solvent is present in a considerable quantity. Thus, Example 10 describes a pigment dispersion which contains, among other things, 10 parts by weight of a copolymer, 15 parts of an ethylene oxide adduct of tall oil fatty acid monoethanol amide reacted with ethylene oxide, 100 parts of tripropylene glycol and 90 parts of water. By adding the copolymer, it is evident that the dispersion is changed from non-fluid, solid paste to pourable form.
The object of the present invention is to provide a homogeneous pigment dispersion which is completely free from organic solvents and which, without causing flocculations which may cause unacceptable differences in color, may be used in water-based paints as well as paints containing organic solvents. A further object is that the included dispersing agents should be easily degradable and have an LC.sub.50 and EC.sub.50 above 1.0 mg/l. These and other objects are realized by the invention embodied by the present claims.